1. Field of the Invention
The present invention relates to an image processing method for analyzing the texture of a surface and a carpet characterized by this method.
2. Description of the Related Art
Traditionally, carpet texture has been characterized by a subjective technique which uses the assessment of panels of expert judges. Such a technique suffers from obvious deficiencies in consistency, including the lack of consistency over time and among differing panel members. Moreover, such a technique lacks an independent method of absolute quantification.
The present invention proposes the use of image processing techniques for the analysis of carpet texture. The image analysis model used in the present invention is based on the second order co-occurrence matrix model originally proposed by Haralick, Shanmugan and Dinstein in an article entitled "Textural Features for Image Classification," IEEE Transactions on Systems, Man and Cybernetics, Vol. SMC-3, No. 6, November 1973, pp. 610-621. This model, known as the Haralick model, examines the statistics of the spatial relationship between gray levels in a homogeneously textured image and calculates a set of textural features which quantify measures such as homogeneity and contrast. The Haralick model has been applied to carpet wear assessment by Siew, Hodgson and Wood as published in an article entitled "Texture Measures for Carpet Wear Assessment," IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 10, No. 1, January 1988, pp. 92-105. This application of the Haralick model differs from the method of the present invention in that no attempt is made to construct a set of normalized textural parameters which are independent of any variations in the instruments used to generate an image of the carpet.
Papers describing image analysis techniques for carpet assessment have been published by the University of Maryland. In an article entitled "New Imaging Techniques for Quantifying Carpet Appearance," Textile Chemist and Colorist, Vol. 23, No. 4, April, 1991, pp. 25-29, Y. Wu of the University of Maryland characterizes the changes in textural appearance of carpet due to wear by carpet tuft size distribution and evenness of tuft spatial distribution. In contrast to the present invention, Wu's method is restricted to a localized analysis. In another article published by the University of Maryland entitled "Assessing Changes in Texture Periodicity Due To Appearance Loss in Carpets: Grey Level Co-Occurrence Analysis," Textile Research Journal, Vol. 61, No. 10, October, 1991, pp. 557-567, by J. Sobus, B. Pourdeyhimi, J. Gerde and Y. Ulcay, the Haralick co-occurrence matrix model was applied to characterizing carpet texture. This work differs from the present invention in that the image analyzed by this work is pre-processed using histogram equalization. Moreover, Sobus et al. do not further construct a set of normalized textural parameters which are linked to the physical properties of carpet and are independent of instrument variations.
The need exists for analyzing the surface texture of a saxony-type carpet, since a large portion of carpets used in residences are cut pile carpets which include saxony-type carpets. In saxony-type carpets, heat-set ply-twisted pile yarn is inserted into a backing material as loops which are then cut to form substantially parallel vertical tufts. The tufts are then evenly sheared to a desired height which is typically medium length. Generally, there are two different styles of saxony-type carpets: 1) a straight-set style in which the fibers at the tuft tip are straight and substantially perpendicular to the plane of the carpet face, and 2) a textured style in which the tufts and the individual fibers have varying degrees of curl.
Yarn which is used as pile in textured saxony-type carpets is prepared by cabling together two or more singles yarns, heat-setting them in their twisted condition, and finally drying them. One known method of processing the ply-twisted yarn prior to making the carpet involves feeding it through a stuffer box, where the yarn is axially compressed, and then passing it through a continuous heat-setting machine, known as a Superba.RTM., which treats the yarn with pressurized, saturated steam to heat-set the twist. Another known method involves feeding the ply-twisted yarn through the stuffer box, and then passing it through a continuous heat setting machine, known as a Suessen, which treats the yarn with dry heat to heat-set the twist.
Depending on the twist level of the yarns and other factors, such as the operating conditions of the stuffer box, textured saxony-type carpets may exhibit different surface textures or appearances. For example, a frieze carpet is made from pile yarns having a "high ply-twist". By the term "high ply-twist" as used herein, it is meant a ply-twist level greater than about 5.5 turns per inch (tpi) (2.17 turns per centimeter (tpc)). When high-ply twist yarn is tufted into a carpet, the tufts demonstrate a highly-kinked and curled effect with gross buckling of the tuft structures. Such a carpet has a surface texture similar to the surface texture shown in FIG. 1. In other instances, a textured saxony-type carpet may have a loose surface texture with open tuft tips forming a brush-like appearance. Such a carpet has a surface texture similar to the surface shown in FIG. 6. This texture approaches the appearance of a straight-set, saxony-type carpet. These carpets are typically made from "low ply-twist" pile yarns. By the term "low ply-twist" as used herein, it is meant a ply-twist level less than about 4.25 turns per inch (1.67 turns per centimeter). Other textured saxony-type carpets are characterized by loose surface textures having open tuft tips, where many of the yarns have an unraveled structure. Such a surface texture is even looser than the texture of the carpet as shown in FIG. 6. These carpets are typically made from "low ply-twist" pile yarns which have been treated by a process where steam is injected directly into the stuffer box.
A textured saxony-type carpet may also be referred to as a "trackless" carpet. Examples of trackless carpet are disclosed in U.S. Pat. No. 4,839,211 to Wilkie et al. and U.S. Pat. No. 5,058,371 to Yu et al. The carpet of Wilkie et al. is made from a blend of conventional carpet fibers (e.g., nylon fibers) and high shrinkage fibers (e.g., acrylic fibers). However, the addition of such high shrinkage fibers causes non-uniformity in the yarn and in the carpet made therefrom.
The carpet of Yu et al. is made of singles yarn having little or no twist which are cabled together. The yarns are prepared by inserting bundles of high shrinkage filaments into a conventional bulked (i.e., crimped) continuous filament singles carpet yarns by means of an air tangler. The yarn is then heatset. During heatsetting of the yarn, the bundles of high shrinkage filaments cause the crimped continuous filament singles carpet yarns to buckle. Some breakage of the high shrinkage acrylic filaments may occur by this method because the acrylic filaments are fragile. Also, as in Wilkie et al., the addition of high shrinkage filaments in the yarn of Yu et al. causes non-uniformity in the yarn and in the carpet made therefrom.
A carpet having a tightly tailored surface texture is a particular type of trackless carpet. The term "tightly tailored surface texture" as used herein means a surface texture characterized by substantially straight and unkinked tufts having a tightly twisted structure, with great twist integrity. The tuft tips are substantially unopened and have compact helical curls, and the tuft structures do not demonstrate gross buckling. This texture is the result of the individual tuft structures having axial compression deformations, similar to the compression of a helical spring and is a particularly desirable texture for a carpet. Thus, there especially exists a need for creating a saxony-type carpet having a tightly tailored surface texture and for analyzing the surface texture thereof.